How do we split our attention?

News

McGill's Cognitive Neurophysiology Lab team finds that we
are natural-born multi-taskers

Imagine you're a hockey goalie, and two opposing players are
breaking in alone on you, passing the puck back and forth. You're
aware of the linesman skating in on your left, but pay him no mind.
Your focus is on the puck and the two approaching players. As the
action unfolds, how is your brain processing this intense moment of
"multi-tasking"? Are you splitting your focus of attention into
multiple "spotlights?" Are you using one "spotlight" and switching
between objects very quickly? Or are you "zooming out" the
spotlight and taking it all in at once?

These are the questions Julio Martinez-Trujillo, a cognitive
neurophysiology specialist from McGill University, and his team set
out to answer in a new study on multifocal attention. They found
that, for the first time, there's evidence that we can pay
attention to more than one thing at a time.

"When we multi-task and attend to multiple objects, our visual
attention has been classically described as a "zoom lens" that
extend over a region of space or as a spotlight that switches from
one object to the other," Martinez-Trujillo, the lead author of the
study, explained. "These modes of action of attention are
problematic because when zooming out attention over an entire
region we include objects of interest but also distracters in
between. Thus, we waste processing resources on irrelevant
distracting information. And when a single spotlight jumps from one
object to another, there is a limit to how fast that could go and
how can the brain accommodate such a rapid switch. Importantly, if
we accept that attention works as a single spotlight we may also
accept that the brain has evolved to pay attention to one thing at
the time and therefore multi-tasking is not an ability that
naturally fits our brain architecture"

Martinez-Trujillo's approach in getting to the bottom of this
long-standing controversy was novel. The team recorded the activity
of single neurons in the brains of two monkeys while the animals
concentrated on two objects that circumvented a third 'distracter'
object. The neural recordings showed that
attention can in fact, be split into two "spotlights" corresponding
to the relevant objects and excluding the in-between
distracter.

"One implication of these findings is that our brain has evolved
to attend to more than one object in parallel, and therefore to
multi-task," said Martinez-Trujillo. "Though there are limits, our
brains have this ability."

The researchers also found that the split of the "spotlight" is
much more efficient when the distractors are very different from
the objects being attended. Going back to the very apt hockey
analogy, Martinez-Trujillo explained that if a Montreal Canadiens
forward is paying attention to two Boston Bruins in yellow and
black, he'll have a more difficult time ignoring the linesmen, also
wearing black, than if he was in a similar situation but facing two
Vancouver Canucks with blue and green uniforms, easily
distinguishable from the linesmen in black'.

In the next generation of experiments, the researchers will
explore the limits of our ability to split attention and multi-task
- looking more closely at how the similarity between objects
affects multi-tasking limits and how those variables can be
integrated into a quantitative model.